Motion Induced by Light: Photokinetic Effects in the Rayleigh Limit

TL;DR

This paper develops a theoretical framework explaining how structured light beams can exert complex, polarization-dependent forces on small objects, revealing new photokinetic effects arising from multipole interference, with implications for optical manipulation.

Contribution

The paper introduces a novel theoretical approach showing that exotic optical forces result from multipole interference, advancing understanding of light-matter interactions in photokinetic effects.

Findings

Exotic optical forces emerge from multipole interference.

Insights into tractor beams and angular momentum interplay.

Orbital-to-spin angular momentum conversion observed.

Abstract

Structured beams of light can move small objects in surprising ways. Particularly striking examples include observations of polarization-dependent forces acting on optically isotropic objects and tractor beams that can pull objects opposite to the direction of the light's propagation. Here we develop a theoretical framework in which these effects vanish at the leading order of light scattering theory. Exotic optical forces emerge instead from interference between different orders of multipole scattering. These effects create a rich variety of ways to manipulate small objects with light, so-called photokinetic effects. Applying this formalism to the particular case of Bessel beams offers useful insights into the nature of tractor beams and the interplay between spin and orbital angular momentum in vector beams of light, including a manifestation of orbital-to-spin conversion.